/****************************************************************************
 *
 * Copyright 2016 Samsung Electronics All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific
 * language governing permissions and limitations under the License.
 *
 ****************************************************************************/
/****************************************************************************
 * kernel/pthread/pthread_condsignal.c
 *
 *   Copyright (C) 2007-2009, 2012 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <tinyara/config.h>

#include <sys/types.h>
#include <pthread.h>
#include <errno.h>
#include <debug.h>

#include "pthread/pthread.h"

/****************************************************************************
 * Definitions
 ****************************************************************************/

/****************************************************************************
 * Private Type Declarations
 ****************************************************************************/

/****************************************************************************
 * Global Variables
 ****************************************************************************/

/****************************************************************************
 * Private Variables
 ****************************************************************************/

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: pthread_cond_signal
 *
 * Description:
 *    A thread can signal on a condition variable.
 *
 * Parameters:
 *   None
 *
 * Return Value:
 *   None
 *
 * Assumptions:
 *
 ****************************************************************************/

int pthread_cond_signal(FAR pthread_cond_t *cond)
{
	int ret = OK;
	int sval;

	svdbg("cond=0x%p\n", cond);

	if (!cond) {
		ret = EINVAL;
	} else {
		/* Get the current value of the semaphore */

		if (sem_getvalue((sem_t *)&cond->sem, &sval) != OK) {
			ret = EINVAL;
		}

		/* If the value is less than zero (meaning that one or more
		 * thread is waiting), then post the condition semaphore.
		 * Only the highest priority waiting thread will get to execute
		 */

		else {
			/* One of my objectives in this design was to make pthread_cond_signal
			 * usable from interrupt handlers.  However, from interrupt handlers,
			 * you cannot take the associated mutex before signaling the condition.
			 * As a result, I think that there could be a race condition with
			 * the following logic which assumes that the if sval < 0 then the
			 * thread is waiting.  Without the mutex, there is no atomic, protected
			 * operation that will guarantee this to be so.
			 */

			svdbg("sval=%d\n", sval);
			if (sval < 0) {
				svdbg("Signalling...\n");
				ret = pthread_sem_give((sem_t *)&cond->sem);
			}
		}
	}

	svdbg("Returning %d\n", ret);
	return ret;
}
